Semiconductor light emitting devices, such as light emitting diodes and laser diodes, include a body of a semiconductor material, generally a group III-V material or a combination of III-V materials, having spaced contacts which allow a current to be passed through the body. Light is generated in the body and can be emitted either from a top or bottom surface of the body, or from an end surface of the body. Laser diodes have a resonator cavity built into the body which creates substantially coherent light which is generally emitted from an end surface of the body. A relatively efficient type of semiconductor light emitting device operates in an injection mode. Such devices include regions of opposite conductivity type with a PN junction therebetween. In such a device, electrons are generated in the N-type region and are injected across the junction into the P-type region where they combine with holes to generate light. The composition of the material used to make the device determines the wavelength of the light emitted from the device.
Gallium nitride (GaN) has been used to make light emitting devices which emit light at different wavelengths, including short wavelengths (visible to ultra-violet). The structures of some light emitting devices which are made of GaN are shown in U.S. Pat. No. 3,683,240 to J. I. Pankove, entitled ELECTROLUMINESCENT SEMICONDUCTOR DEVICE OF GAN, issued Aug. 8, 1972 and U.S. Pat. No. 3,740,622 to J. I. Pankove et al, entitled ELECTROLUMINESCENT SEMICONDUCTOR DEVICE FOR GENERATING ULTRA VIOLET RADIATION, issued June 19, 1973. However, a problem with GaN is that it cannot be made highly conductive P-type. Therefore, it has been difficult to make an injection mode light emitting device from gallium nitride.